Note 5 - Accrued Liabilities - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accrued interest	$ 980	$ 0
Accrued payroll and other related expenses	556	495
Deferred revenue - subscription rental program	498	448
Accrued clinical trial costs	378	337
Accrued bonuses	303	1,209
Accrued professional fees	162	120
Other accruals	265	219
Total accrued liabilities	3,376	3,053
Accrued Liabilities [Member]
Current operating lease liabilities	$ 234	$ 225